There have been developed electroluminescent devices using organic thin films. Such electroluminescent devices using organic thin films, namely, organic electroluminescent devices each generally include a substrate bearing an anode, a cathode, and one or more organic layers. The one or more organic layers are arranged between the two electrodes and include at least a light-emitting layer. Such organic layers may include a hole injection layer (anode buffer layer), a hole transport layer, a hole blocking layer, an electron transport layer, and an electron injection layer, in addition to a light-emitting layer. These layers are generally arranged or laminated between the anode and the cathode to constitute an organic electroluminescent device.
Organic electroluminescent devices have used fluorescence emission. As an attempt to raise luminous efficiency of the devices, it has also been examined to use phosphorescence instead of fluorescence. Sufficient luminous efficiency, however, has not yet been obtained even when phosphorescent emission is used.
For example, Appl. Phys. Lett., 75, 4 (1999) discloses the following biphenyl derivative as a host material.

However, an organic electroluminescent device using the biphenyl derivative does not yield a satisfactorily high luminous efficiency, because the recombination of charge tends to occur unevenly in the vicinity of the cathode, and the device has poor balance in charge recombination.
Japanese Unexamined Patent Application Publication No. 6-1972 discloses an organic electroluminescent device using the following compound:

The compound, however, shows light emission only under a high voltage and is supposed to be insufficient in luminance and luminous efficiency.
Japanese Unexamined Patent Application Publications No. 2000-186066 and No. 2000-169448 propose, as hole transporting materials and light-emitting layer materials for fluorescent emitting devices or for electrophotographic photoreceptors, pyridine compounds typified by the following compounds:

Japanese Unexamined Patent Application Publication No. 2003-22893 discloses, as a material for organic electroluminescent devices, the following compound:

PCT International Publication Number WO 03/078541 discloses, as materials for organic electroluminescent devices, the following compounds:

The compounds described in these patent documents, however, show a significant polarization of charge in the molecule and have a relatively low triplet excitation level, because they have such a structure as to enable the conjugation of a nitrogen atom on the pyridine ring, triazine ring, pyrimidine ring, or pyrazine ring with a nitrogen atom on the carbazole ring. In addition, they have a poor durability as materials for organic electroluminescent devices. Accordingly, they are insufficient in performance for use in blue-light emitting devices and phosphorescent emitting devices. In addition, the compounds show a poor electrochemical durability when they are not fully substituted at the 2-, 4-, and 6-positions of the pyridine ring, at the 2-, 4-, and 6-positions of the pyrimidine ring, or at the 2-, 3-, 5-, and 6-positions of the pyrazine ring.
PCT International Publication Number WO 03/080760 discloses the following compounds as materials for organic electroluminescent devices.

These compounds, however, are susceptible to localization of positive or negative charges when the molecules are subjected to electric oxidation or reduction. This is because, in these compounds, two carbazolyl groups serving as electron-donating groups are substituted on one aromatic ring (a benzene ring herein) at such positions (the meta-position) as to prohibit the conjugation with each other through the aromatic ring. The compounds having such a partial structure have a poor durability against electric oxidation and reduction. Even though the compounds further include a pyridine ring or a pyrimidine ring in order to improve the durability against electric reduction, the pyridine ring and the pyrimidine ring still have a decreased durability against electric reduction. This is because the aromatic ring (benzene ring herein) substituted with two carbazolyl groups is located at the para-position with respect to the nitrogen atom of the pyridine ring and the pyrimidine ring, the aromatic ring is so located as to enable the conjugation with the pyridine ring and the pyrimidine ring, and the aromatic ring acts to give electrons to the pyridine ring and the pyrimidine ring.
PCT International Publication Number WO 03/080760 also discloses the following compound:

This compound is expected to have an improved durability against electric oxidation, but has a poor hole transporting ability, because it has only one carbazolyl group. Accordingly, the compound is not in good balance between the hole transporting ability and the electron transporting ability and is not suitable as a host material for a light-emitting layer of an organic electroluminescent device. In addition, it has a poor thermal stability.